Photosemiconductor devices incorporating photosemiconductor elements such as LEDs (Light Emitting Diodes) and fluorescent materials have high energy efficiency and long life spans, and are therefore used in outdoor displays, portable liquid crystal backlights, vehicle devices and the like, with ever increasing demand. With the advances in high luminance of LED devices, it has become a goal to prevent deterioration of photosemiconductor devices due to increased junction temperature caused by increased element heat generation or by increased direct light energy.
Patent document 1 discloses a photosemiconductor element mounting board employing a thermosetting resin composition that comprises an epoxy resin and a curing agent such as an acid anhydride.
Acid anhydrides are commonly used as curing agents for epoxy resins. They are also used as starting materials to obtain polyimide compounds by reaction with diamines. Acid anhydrides are inexpensive and superior from the standpoint of transparency, electrical insulating properties, chemical resistance, humidity resistance and adhesion. Acid anhydrides are therefore used for a variety of purposes including electrical insulating materials, semiconductor device materials, photosemiconductor sealing materials, adhesive materials and coating materials.
One class of acid anhydrides is that of polycarboxylic anhydrides formed by polycondensation of polyvalent carboxylic acids. For example, polycarboxylic anhydrides obtained by dehydrating condensation reaction between aliphatic dicarboxylic acid molecules such as polyazelaic acid or polysebacic acid are sometimes used as curing agents or curing accelerators for thermosetting resins such as epoxy resins, melamine resins and acrylic powder coatings. The polycarboxylic anhydrides obtained by dehydrating condensation reaction between aliphatic dicarboxylic acid molecules are useful as curing agents for powder coatings or casting resins because they readily yield cured products exhibiting excellent flexibility and thermal shock resistance.
Incidentally, other uses of acid anhydrides include biomedical applications as proposed in Patent document 2, which employs a high molecular weight polycarboxylic anhydride (polyvalent carboxylic acid condensate) with an average molecular weight exceeding 20000, obtained by condensation between aliphatic and aromatic dicarboxylic acid molecules.    [Patent document 1] JP 2006-140207 A    [Patent document 2] JP 63-258924 A